This invention relates to an oil changer which is capable of extracting or drawing oil from an external oil reservoir such as, for example, an oil sump for engine oil on an automobile to compare the oil drawn with fresh oil for visually inspecting the contamination degree of the oil and if oil change is necessary, of immediately changing such contaminated oil with fresh oil, thus performing, by the use of a single oil changer, the three functions of extraction, contamination inspection and exchange of oil.
Conventionally, oil such as automobile engine oil, for example, when used for a certain time, is usually changed with fresh oil without inspecting the contamination or deterioration degree of such oil. For this reason, oil once used has often been discarded even where it is still usable for normal service, resulting in unnecessary or exccessive oil consumption. Further, because of absence of any convenient and effective measure for inspection of oil contamination, oil changing operations have heretofore been very troublesome and ineffective.